This honestly depends on which errors you're receiving.
: If CMake cannot find GIT on your system, that is probably because you didn't install it correctly. This can easily be bypassed if you reinstall git correctly. Here is a tutorial about it. Or, you can view this thread for more help.
: This is caused by you not supplying the correct source path. You need to set the source path to the main CMakeLists.txt located in TrinityCore/ folder. View this post for more clarification.
: These "Unknown" errors could possibly be because you aren't using the latest compiler. You need to use VS 2013 and install VS 2013 Redistributable Packages. TC no longer supports VS 2008, 2010, 2011 or 2012.
: You need to select Visual Studio 12 (or greater) when you're configuring the compiler. If you do not see Visual Studio 12 (or greater) in the drop down menu, go to the CMake website, download CMake and install it again. Afterwards, you should be able to see Visual Studio 12 (or greater).
If you're receiving the error "This version of Visual Studio reviews a newer version of Windows" when installing VS 2013, go to this FAQ item for more help.
If you're needing more help on how to work with CMake, go to this thread.